This invention relates to a metal-cased electrolytic capacitor, and more particularly to such a capacitor in which the capacitance section does not fill the metal case.
Improvements in the manufacture and processing of electrode foils for use in electrolytic capacitors have resulted in foils that offer higher capacitance, which has led directly to a reduction in the size of capacitance sections that are required for a given capacitance rating. This development, in turn, has led to smaller finished capacitors being offered to the market.
However, some end-equipment manufacturers require specific physical sizes for capacitors so that they will not need to redesign their electronic products and/or retool their wiring board insertion equipment in order to use smaller capacitors. On the other hand, inasmuch as capacitance sections account for 70 to 80% of total capacitor cost, capacitor manufacturers do not wish to make sections for a given capacitance rating which are larger than they need to be.
It is known in the prior art to roll a series of capacitance sections to the same diameter (same length of foil) but different widths (height of section) in order to provide a series of different capacitances in a given diameter can. Such is taught by Kolkowski in U.S. Pat. No. 4,164,006 issued Aug. 7, 1979. However, in the correlated capacitors of Kolkowski, the capacitance section extends to and is supported by the bottom of a can of proper height.
It is also known in the prior art to roll a capacitance section to a given diameter on different arbor sizes providing a hole extending longitudinally through the capacitor section. It is also known to indent can housings so as to provide lateral support for capacitance sections. Both concepts are taught by Elias and Granger in U.S. Pat. No. 4,352,147 issued Sept. 28, 1982. Again, the capacitor section of Elias et al extends to the bottom of the metal can housing and is supported thereby.